Field of the Invention
The present invention relates to an image pickup apparatus in which a shooting direction is changeable and a control method thereof.
Description of the Related Art
Conventionally, network cameras capable of controlling a camera according to a remote operation and monitoring a video via a network or a dedicated line are known. For example, there is an apparatus having a movable unit in which a camera head performs a pan (horizontal rotation) operation and a tilt (vertical rotation) operation and shooting is possible in a wide range. Further, there is an endless turning type in which rotation is possible without limitation in a range of 360 degrees without a mechanical end in the movable unit which performs the pan operation. In addition, there are a preset cyclic moving function and a privacy mask function as functions of the network camera. The preset cyclic moving function is a function of registering pan and tilt positions to be monitored by a user as preset positions in advance and cyclically moving and monitoring the registered preset positions. The privacy mask function is a function of superimposing a rectangular image on a partial region desired to be masked by the user in a shooting region to process a captured image so that the partial region is not viewed. In order to improve the performance of these functions, the improvement of stop position accuracy of the pan/tilt movable unit is required.
In the endless turning type network camera, there is an apparatus in which the movable unit for performing the pan operation rotates without limitation and a movable angle of the movable unit for performing the tilt operation is 180 degrees. Because a degree of freedom of the movable unit is high, the movable unit can be directed fully backward at 180 degrees through the pan operation and the movable unit can also be directed fully backward at 180 degrees through the tilt operation. In addition, at the time of rotating from the camera head position at which the tilt angle is 0 degrees to the camera head position at which the tilt angle is −180 degrees, the camera head turns upside down, resulting in a video in which the sky and the earth are reversed. Because users are uncomfortable watching videos in which the sky and the earth are reversed, there is an apparatus having a function (automatic flip) of outputting a video of a state in which the sky and the earth are in their correct positions by automatically reversing the video through an electronic process according to the tilt angle. For example, shooting is possible in the same shooting direction and the same sky and earth directions of the video between a camera head position of a tilt of 0 degrees at a pan of 180 degrees and a camera head position of a tilt of −180 degrees at a pan of 0 degrees. In the case of the endless turning type network camera, there are two positions which are in the same shooting direction but differ in positions of the movable unit. For a stop position error between the two different positions, there are more causes of the error than with a stop position error for one position. Thus, when the error is comparatively large, the stop position error of the movable unit occurs. For example, a shift is likely to occur in the shooting direction of a preset position in the preset cyclic moving function and a shift is likely to occur at a drawing position of a privacy mask.
In Japanese Patent Laid-Open No. 2005-303806, a method of performing accurate preset shooting even when the accuracy of a movement mechanism is low is disclosed. This method is a method of adjusting a trimming region so that trimming mark information registered at the time of preset position registration is reproduced after moving to a registered preset position at the time of returning to the preset position. In addition, in the publication of Japanese Patent Laid-Open No. 2000-83188, a method in which monitoring is also performed in an opposite direction by automatically turning a camera head in a horizontal direction 180 degrees according to the pan operation when the camera head moves in a vertical direction according to the tilt operation and is directed directly downwardly is disclosed.
In the conventional technology disclosed in Japanese Patent Laid-Open No. 2005-303806, image processing is necessary when the trimming region is adjusted so that registered trimming mark information is reproduced. Thus, processing load and processing time are necessary according to the image processing. In addition, because the trimming process is performed, a shooting range of an image to be distributed is narrowed for an imaging range of an imaging element. In addition, in conventional technology disclosed in the publication of Japanese Patent Laid-Open No. 2000-83188, a problem of the stop position error between the above-described two positions (two positions which are in the same shooting direction but differ in positions of the movable units) does not occur because an automatic flip operation is performed according to the rotation of the movable unit rather than the rotation of the image. However, a period in which control is difficult or a period in which monitoring is difficult occurs while a reversing operation of the movable unit occurs in the automatic flip according to the rotation of the movable unit. Thus, as compared with the automatic flip by image rotation, there is concern of the controllability or monitor ability being impaired.
In addition, when the privacy mask is drawn, it is necessary to follow a drawing position according to a change in the shooting direction in association with the pan/tilt operation. That is, an error of pan/tilt position information to be used in the drawing of the privacy mask becomes a cause of the drawing position error of the privacy mask.